Macroevolutionary trends in theropod dinosaur feeding mechanics

Area of Science:

• Paleontology
• Evolutionary Biology
• Biomechanics

Background:

• Theropod dinosaurs exhibited significant dietary shifts throughout their evolutionary history, from carnivory to herbivory and back.
• Mandibular morphology is crucial for understanding feeding adaptations, yet previous studies were often limited in scope or methodology.
• The relationship between macroevolutionary changes and ontogenetic patterns in theropod mandibles remains underexplored.

Purpose of the Study:

• To investigate functional morphological patterns in theropod mandibular evolution and compare them to ontogenetic trajectories.
• To analyze how feeding mechanics vary across different theropod dietary groups and major clades using finite element analysis.
• To explore the potential link between evolutionary changes in mandibular structure and developmental processes.

Main Methods:

• Finite element analysis (FEA) was employed to study the mandibles of non-avialan coelurosaurian theropods.
• Feeding-induced stresses were analyzed across various dietary groups and major clades.
• An ontogenetic series of tyrannosaurid jaws (Tarbosaurus and Tyrannosaurus) was examined to compare developmental and evolutionary patterns.

Main Results:

• A consistent reduction in feeding-induced stresses was observed across theropod lineages over time.
• Mandibular adaptations included post-dentary expansion and specific dentary curvature (downturned in herbivores, upturned in carnivores), likely via the "curved bone effect."
• Similar stress reduction patterns were found in the ontogenetic series of tyrannosaurids, attributed to bone functional adaptation.

Conclusions:

• Theropod mandibular evolution shows a general trend of structural strengthening, irrespective of diet, potentially driven by functional adaptation.
• The observed evolutionary trend in mandibular mechanics parallels ontogenetic changes, suggesting a phenomenon akin to "functional peramorphosis."
• These findings highlight the interplay between developmental processes and macroevolutionary trends in shaping vertebrate feeding structures.